Ultrasonic peening treatment of assembled components

ABSTRACT

Ultrasonic peening treatment is desirable where an application of a compressive stress is helpful to reduce the incidence of crack formation on highly stressed parts. Ultrasonic peening treatment can be performed in field applications without requiring a rotor to be removed from the machine. The system includes an acoustic element that excites peening media within a peen chamber. A frame is attachable to an assembled turbine rotor component and includes support structure engageable with the acoustic element. The frame is cooperable with a chamber tooling that defines and encloses the peen chamber together with the turbine rotor component.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is the U.S. national phase of International ApplicationNo. PCT/US2006/018469 filed 12 May 2006 which designated the U.S. andclaims priority to U.S. Provisional Patent Application Ser. No.60/680,039 filed 12 May 2005, the entire contents of each of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to peening of assembled rotor parts whilestill in the casing or unit rotor and, more particularly, to ultrasonicpeening treatment of rotor components for gas turbines, steam turbinesor hydro machines wherever shot peening is deemed necessary ordesirable.

It is generally recognized that fatigue life for certain materials isenhanced when parts are shot peened. Peening induces a residualcompressive stress that retards crack initiation. The most widely usedpeening technology involves a large quantity (many pounds) of smallsized metallic or ceramic ‘shot,’ which is propelled at the component tobe peened. In a shop environment, the small shot can be fairly easilycleaned from the component to avoid having it introduced into a workingturbine.

In instances where rotor parts are repaired or modified in the field,parts may be required to be re-shot peened in order to introduce thecompressive stress to resist cracking upon return to service. In a fieldapplication, however, a conventional shot peen process scatters shotwidely about the work area, and the small pieces of shot are not easilyretrieved from the turbine unit. Residual shot in the unit poses athreat to the operation of the turbine.

Forms of peening other than conventional exist, such as laser shock,water cavitation shock, and the like; however, these forms are eithervery expensive or not readily field adaptable.

Ultrasonic peening is a commercially available technology that generallyuses a fixed computer-controlled machine in a shop environment to peencomponents of a fixed shape. This configuration generally requireseither (1) the components to be a maximum size (such as a piece part),or (2) the machinery to be large scale in order to treat the componentas specified. Existing applications of peening on rotor componentstypically perform the operation with separate pieces comprising therotor rotating to the peening equipment or the peening equipmentmanipulating around the separate parts in a horizontal plane. As aconsequence, the existing applications are not suitable for use in situ.Additionally, the existing applications lack equipment mobility and aretypically unable to operate on a vertically rotating component.

Additionally, other shot peening methods (e.g., conventional, water jetcavitation, laser) require a “line-of-sight” such that the media doingthe peening (metal or ceramic shot, water jet, laser beam) must be inline with the object to be peened or be able to ricochet and peen thesurface of interest therein. With most processes, a line-of-sight is notavailable while the rotor is still in the casing and/or the rotorassembly is still intact.

An additional concern with conventional shot peening is that some of theshot would remain in the assembled rotor or casing, causing subsequentpremature failure of other parts, such as buckets, nozzles or bearings,upon return to service. It would thus be desirable to enable a rotorcomponent to be peened without disassembly and without potentialcontamination by shot media.

BRIEF DESCRIPTION OF THE INVENTION

In an exemplary embodiment of the invention, a system for ultrasonicpeening treatment of assembled turbine rotor components includes anacoustic element that excites peening media within a peen chamber, and aframe attachable to an assembled component. The frame includes supportstructure engageable with the acoustic element, where the frame iscooperable with a chamber tooling that defines and encloses the peenchamber together with the assembled component.

In another exemplary embodiment of the invention, a method forperforming ultrasonic peening treatment of assembled turbine rotorcomponents includes the steps of attaching a frame to an assembledcomponent; securing an acoustic element that excites peening mediawithin a peen chamber to the frame; enclosing the peen chamber with achamber tooling selectively engageable with the frame and the assembledcomponent, the chamber tooling defining and enclosing the peen chambertogether with the assembled component; and activating the acousticelement.

In still another exemplary embodiment of the invention, a system forultrasonic peening treatment of an assembled turbine rotor wheelincludes a frame attachable to the turbine rotor wheel and spanningcircumferentially across at least three of the dovetail slots. The frameincludes an attachment member shaped corresponding to the dovetail slotsfor axial sliding attachment to the rotor wheel. An acoustic element issecurable to the frame that excites peening media within a peen chamber.At least two insert members are selectively engageable with the rotorwheel through the frame and the dovetail slots on either side of theattachment member, where the insert members define and enclose the peenchamber together with the turbine rotor wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section of a turbine rotor wheel with attached ultrasonicpeening treatment system;

FIG. 2 illustrates the assembly process for securing the system to therotor wheel;

FIG. 3 shows a cooling groove of the rotor wheel;

FIG. 4 is a closer view of the insert members;

FIG. 5 illustrates a tooling for delivering or removing peening mediafrom the peen chamber;

FIG. 6 illustrates the system with the attached acoustic element; and

FIG. 7 shows exemplary structure for ensuring that all peening media isremoved from the peen chamber.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 2, a system for ultrasonic peeningtreatment of assembled turbine rotor components includes a frame 12attachable to an assembled turbine rotor component. The rotor componentshown in FIGS. 1 and 2 is a section of a turbine wheel 14. A typicalturbine wheel 14 includes a plurality of dovetail slots 16 that receivecorrespondingly-shaped dovetails of turbine blades (not shown). Theframe 12 includes a dovetail-shaped attachment 18 that slides axiallyinto a dovetail slot 16 on the rotor wheel 14. Screws or other suitablesecuring structure fix the frame 12 in the slot 16.

As shown in FIG. 2, at least one insert member 20, possibly two orthree, is selectively engageable with the frame 12 and the rotor wheel14. More particularly, as shown in FIG. 3, the rotor wheel 14 includes acooling passage defined by a cooling groove 22 extendingcircumferentially around the rotor wheel 14 and by an aperture 24 ineach of the dovetail slots 16 opening to the cooling groove 22. Theframe 12 is provided with multiple apertures 26 that are spaced fromeach other corresponding to a space between each of the dovetail slots16. The frame 12 is positioned on the rotor wheel 14 such that theapertures 26 are disposed in alignment with the dovetail slots 16. Inthis manner, the insert members 20 include an articulated shaft 28 thatis extendible through the aperture 26 in the frame 12 and into thecooling groove 22 through the aperture 24.

As shown in FIG. 4, the insert members 20 are generally formed of thearticulated shaft 28 including an insert leg 30 and a pivot leg 32.During assembly, the insert leg 30 and the pivot leg 32 are generallyaligned to define a straight shaft for insertion through the apertures26 and the frame 12. After the articulated shaft 28 is inserted throughthe frame 12 and through aperture 24 in the dovetail slot 16, anadjusting mechanism 34 is actuated to pivot the pivot leg 32 relative tothe insert leg 30 such that the pivot leg 32 engages the cooling groove22 of the rotor wheel 14. Any suitable gearing structure or the like maybe utilized to cause the pivot leg 32 to pivot when the adjustingmechanism 34 is rotated. In this manner, the insert member 20 includingthe articulated shaft 28 serves to define and enclose a peen chambertogether with the rotor wheel 14. In a preferred embodiment, withcontinued reference to FIG. 4, the pivot legs 32 of adjacent insertmembers 20 are pivoted into engagement with the cooling groove 22 in apreset order and include respective grooves 36 to cooperatively define aportion 38 of the peen chamber.

With the insert members 20 secured to the frame 12 and the pivot legs 32secured in the cooling groove 22, a peen chamber is defined with therotor wheel 14 that is entirely enclosed such that peening media withinthe peen chamber are prevented from escaping the peen chamber. In otherarrangements such as those without a cooling groove, the insert membersmay be unnecessary where the enclosed peen chamber can be defined viasuitable tooling or the like.

Once the frame 12 is secured in place, and the insert members 20 arepositioned and configured to define the peen chamber, the unit is readyto perform the ultrasonic peening treatment. The frame 12 includessupport structure 40 in communication with the peen chamber thatreceives various tooling for use and operation of the system. FIG. 5illustrates an exemplary tooling 42 coupled with the support structure40 for delivering a preset number of peening media into the peenchamber. The tooling 42 is meant to be generic as peening media can beintroduced into the peen chamber in multiple ways, including via a toolwith a plunger, being poured into the chamber, etc.

After delivering peening media to the peen chamber, the delivery tooling42 is removed, and an acoustic element 44 (see FIG. 6) is coupled withthe support structure 40 and activated to excite the peening mediawithin the peen chamber. The use and operation of the acoustic element44 are known, and further details thereof will not be described.

After the peening treatment is complete, the acoustic element 44 isremoved, and a removal tooling 43 (FIG. 5) for removing peening mediafrom the peen chamber is attached to the support structure 40. Thetooling 43 for removing peening media includes structure for ensuringthat the preset number of peening media is removed from the peenchamber. For example, the removal tooling 43 may incorporate a gridframe 48 as shown in FIG. 7. The grid frame 48 receives the peeningmedia via the removal tooling 43 and includes a plurality of apertures49, one each for each member of the peening media. In this manner, theoperator can quickly and easily make a visual determination of whetherall of the peening media has been removed form the peen chamber. In oneexemplary embodiment, the removal tooling 43 utilizes a vacuum structurefor removing peen from the peen chamber.

Although the description herein provides details of an application toultrasonic peening treatment of a turbine rotor wheel, the invention isnot necessarily meant to be limited to this application. Rather, thesystem and method are applicable to ultrasonic peening on steam, gas orhydro turbine rotor components where application of a compressive stressis desirable to reduce the incidence of crack formation on highlystressed parts. The treatment system and method allow for theapplication of ultrasonic peening to be performed in field applicationswithout requiring removal of the rotor from the machine. In analternative exemplary application, the system could be utilized forpeening the area of the lock wire tabs of a turbine bucket dovetail. Inthis instance, the peen chamber would be defined and enclosed by thetooling around the dovetail post, and excitement of the peening mediacould be carried out in the same manner as discussed above.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A system for ultrasonic peening treatment of assembled components, the system comprising: an acoustic element that excites peening media within a peen chamber; a frame attachable to an assembled component, the frame including support structure engageable with the acoustic element, wherein the frame is cooperable with a chamber tooling that defines and encloses the peen chamber together with the assembled component; and a peen insert tooling engageable with the frame support structure, the peen insert tooling delivering a preset number of peening media into the peen chamber.
 2. A system according to claim 1, further comprising a peen removal tooling engageable with the frame support structure, the peen removal tooling removing peening media from the peen chamber, wherein the peen removal tooling comprises a counter that ensures that the preset number of peening media is removed from the peen chamber.
 3. A system according to claim 2, wherein the counter comprises a grid frame including an aperture for each of the preset number of peening media.
 4. A system according to claim 1, wherein the assembled component comprises a turbine rotor wheel including a plurality of dovetail slots, and wherein the frame comprises a dovetail attachment shaped corresponding to the wheel dovetail slots for axial sliding attachment to the rotor wheel.
 5. A system for ultrasonic peening treatment of assembled components, the system comprising: an acoustic element that excites peening media within a peen chamber; and a frame attachable to an assembled component, the frame including support structure engageable with the acoustic element, wherein the frame is cooperable with a chamber tooling that defines and encloses the peen chamber together with the assembled component, wherein the assembled component comprises a turbine rotor wheel including a plurality of dovetail slots, and wherein the frame comprises a dovetail attachment shaped corresponding to the wheel dovetail slots for axial sliding attachment to the rotor wheel, wherein the chamber tooling comprises at least one insert member selectively engageable with the frame and the turbine rotor wheel, wherein the rotor wheel further includes a cooling passage defined by a cooling groove extending circumferentially around the rotor wheel and by an aperture in each of the dovetail slots opening to the cooling groove, and wherein the insert member is extendable through the frame and into the cooling groove through the aperture.
 6. A system according to claim 5, wherein the insert member comprises an articulated shaft having an insert leg and a pivot leg, the pivot leg being selectively pivotable relative to the insert leg, wherein the insert leg and the pivot leg are extendable through the frame and through the aperture, and the pivot leg is subsequently pivotable to engage the cooling groove.
 7. A system according to claim 6, comprising two insert members extendable through the frame and into the cooling groove on opposite sides of the dovetail attachment, wherein the pivot legs of the insert members are pivotable to engage the cooling groove and cooperatively define a portion of the peen chamber.
 8. A method for performing ultrasonic peening treatment of assembled components, the method comprising: attaching a frame to an assembled component; securing an acoustic element that excites peening media within a peen chamber to the frame; enclosing the peen chamber with a chamber tooling selectively engageable with the frame and the assembled component, the chamber tooling defining and enclosing the peen chamber together with the assembled component; and activating the acoustic element, wherein the assembled component comprises a turbine rotor wheel including a plurality of dovetail slots, and wherein the frame includes a dovetail attachment shaped corresponding to the wheel dovetail slots, the attaching step being practiced by axially sliding the dovetail attachment one of the dovetail slots of the rotor wheel, wherein the chamber tooling comprises at least one insert member, and wherein the rotor wheel further includes a cooling passage defined by a cooling groove extending circumferentially around the rotor wheel and by an aperture in each of the dovetail slots opening to the cooling groove, the enclosing step comprising extending the insert member through the frame and into the cooling groove through the aperture.
 9. A method according to claim 8, further comprising, prior to the securing step, delivering a preset number of peening media into the peen chamber.
 10. A method according to claim 9, further comprising, after the activating step, removing peening media from the peen chamber with peen removal tooling, and ensuring that the preset number of peening media is removed from the peen chamber.
 11. A method according to claim 8, wherein the insert member comprises an articulated shaft having an insert leg and a pivot leg, the pivot leg being selectively pivotable relative to the insert leg, the enclosing step further comprising extending the insert leg and the pivot leg through the frame and through the aperture, and subsequently pivoting the pivot leg to engage the cooling groove.
 12. A method according to claim 11, wherein the enclosing step comprises extending two insert members through the frame and into the cooling groove on opposite sides of the dovetail attachment, and pivoting the pivot legs of the insert members to engage the cooling groove and cooperatively define a portion of the peen chamber.
 13. A system for ultrasonic peening treatment of an assembled turbine rotor wheel, the rotor wheel including a plurality of dovetail slots for receiving bucket dovetails of turbine buckets, the system comprising: a frame attachable to the turbine rotor wheel and spanning circumferentially across at least three of the dovetail slots, the frame including an attachment member shaped corresponding to the dovetail slots for axial sliding attachment to the rotor wheel; an acoustic element securable to the frame, the acoustic element exciting peening media within a peen chamber; and at least two insert members selectively engageable with the rotor wheel through the frame and the dovetail slots on either side of the attachment member, the insert members defining and enclosing the peen chamber together with the turbine rotor wheel. 